ABSTRACT Open defecation contaminates ambient environment and water sources with pathogenic bacteria and may, over time, decrease vaccine efficacy and increase childhood malnutrition. Prolonged exposure to fecal pathogens causes a condition called environmental enteropathy, which is characterized by malabsorption, atrophy of intestinal villi, crypt hyperplasia, T-cell infiltration and inflammation of the jejunum. These changes can diminish a vaccine-specific response, or destroy an attenuated vaccine by an aggressive local immune response in the digestive tract. Furthermore, hyperplasia or thickening of small intestine walls may obstruct proper absorption of nutrients, leading to malnutrition. However, alarmingly few community interventions with strong study designs quantify the relation between open defecation, vaccine efficacy, diarrhea and child malnutrition. We propose a state and district-level analysis of India's national disease surveillance and regional survey data from two-time periods, 2013 and 2016, to estimate this relation by using as a natural experiment India's national sanitation campaign, Swachh Bharat Mission (SBM). SBM is a restructured version of India's Total Sanitation Campaign (TSC), which was originally initiated in 1999, but revamped in 2014 with the goal of complete eradication of open defecation, and installation of toilets in every household across the country by 2019. The election of a new federal government in 2014 brought in a strong, national mandate on sanitation and hygiene. According to national estimates, > 10 million toilets have been constructed thus far, with an annual funding of over $ 1 billion allotted exclusively towards SBM. We hypothesize that increased toilet construction owing to implementation of SBM by India's newly elected central government (in 2014) precedes a reduction in vaccine preventable illnesses (diphtheria, pertussis, tetanus and measles), diarrhea and malnutrition (stunting, wasting and underweight) in children less than 5 years of age. We further aim to test the association between political impetus towards SBM implementation and child health outcomes using data on state and district level utilization of government funding allocated for SBM. We will use high-quality data from India's Demographic and Health Survey (comprising District Level Household & Facility Survey, Annual Health Survey, and National Family Health Survey) and national administrative Health Surveillance Reports to achieve our study Aims. The results of this study may hold strong implications for control of diarrheal diseases and vaccine efficacy. Our collaboration with the Indian Institute of Management Bangalore (IIMB), moreover, on this topic aligns well with NIH's Indo-US Vaccine Action Program (VAP) Small Research Grant's stated goal of supporting collaborative vaccine-related research that may ultimately reduce the burden of infectious diseases in India.